JP7110819B2 - INKJET IMAGE FORMING APPARATUS AND CONTROL DEVICE FOR INKJET IMAGE FORMING APPARATUS - Google Patents

Description

The present invention relates to an inkjet image forming apparatus and a control device for the inkjet image forming apparatus, and more particularly, by measuring the acceleration of a carriage unit on which an inkjet head is mounted, the pressure fluctuation of the ink in the flow path leading to the nozzles can be accurately measured. The present invention relates to an inkjet image forming apparatus that can be grasped and a control device for the inkjet image forming apparatus.

2. Description of the Related Art There has been proposed an inkjet image forming apparatus that forms an image on a recording medium by ejecting ink from nozzles of an inkjet head using an electromechanical conversion action of a piezoelectric element. In an inkjet image forming apparatus, when a nozzle ejects ink downward, a negative pressure is applied to the ink in the nozzle, and the surface tension of the ink causes the ink to flow into the nozzle against gravity. trying to stay.

The inkjet head is moved to a position close to the recording medium when forming an image. At this time, vibrations and shocks applied to the inkjet head cause pressure fluctuations in the ink inside the nozzles and in the channels that supply the ink to the nozzles. air may enter the nozzle. If air enters the nozzles in this manner, ink cannot be ejected, resulting in printing defects (missing dots).

Japanese Unexamined Patent Application Publication No. 2002-200002 describes an image forming apparatus in which an accelerometer is provided in a carriage unit on which an inkjet head is mounted. In this image forming apparatus, the acceleration in the ink ejection direction is measured by an accelerometer, and ink ejection is restored when the measured acceleration exceeds a threshold value and dot dropout occurs.

Japanese Patent Application Laid-Open No. 2002-200001 also describes an image forming apparatus in which an accelerometer is provided in a carriage unit. In this image forming apparatus, acceleration is measured by an accelerometer, and when the measured acceleration exceeds a threshold value, the cause of malfunction of the carriage unit is identified.

Japanese Patent Application Laid-Open No. 2007-001160 JP 2017-056604 A

By the way, the flow paths from the ink tanks to the nozzles in the inkjet head are not necessarily parallel to the direction of ink ejection or the moving direction of the carriage unit, nor are they necessarily linear. This is because, in many cases, it is not possible to provide a straight flow path in order to achieve both high-density image formation and miniaturization of the apparatus.

If the shape of the flow path leading to the nozzle is complicated, it is not possible to accurately grasp the pressure fluctuation of the ink in the flow path only by measuring the acceleration in the ink ejection direction. If the ink pressure fluctuations cannot be accurately grasped, the vibrations and shocks applied to the carriage unit cannot be sufficiently reduced, and ejection failure cannot be prevented. There is a problem that the size is reduced, and the time required for image formation is lengthened more than necessary.

SUMMARY OF THE INVENTION Accordingly, an object of the present invention is to provide an inkjet image forming apparatus and an inkjet image forming apparatus capable of accurately grasping pressure fluctuations of ink in flow paths leading to nozzles by measuring the acceleration of a carriage unit on which an inkjet head is mounted. The object is to provide a control device.

Furthermore, other objects of the present invention will become clear from the following description.

The above problems of the present invention are solved by the following inventions.

1.
a carriage unit mounted with an ink ejecting portion and a channel member forming a channel for supplying ink to the ink ejecting portion;
driving means for moving the carriage unit to a predetermined printing position during printing;
An inkjet image forming apparatus, wherein the carriage unit is equipped with an accelerometer capable of measuring acceleration in two orthogonal xy-axis directions.
2.
A control means for controlling the driving means,
The control means controls the product of the acceleration in the x-axis direction detected by the accelerometer and the flow difference in the x-axis direction, and the acceleration in the y-axis direction and the flow difference in the y-axis direction detected by the accelerometer. 2. The inkjet image forming apparatus according to 1, wherein the acceleration of the carriage unit is reduced when the sum exceeds a predetermined threshold value.
3.
a carriage unit mounted with an ink ejecting portion and a channel member forming a channel for supplying ink to the ink ejecting portion;
driving means for moving the carriage unit to a predetermined printing position during printing;
An inkjet image forming apparatus, wherein the carriage unit is equipped with an accelerometer capable of measuring acceleration in three orthogonal xyz-axis directions.
4.
A control means for controlling the driving means,
The control means controls the product of the acceleration in the x-axis direction detected by the accelerometer and the flow difference in the x-axis direction, and the acceleration in the y-axis direction and the flow difference in the y-axis direction detected by the accelerometer. and the product of the acceleration in the z-axis direction detected by the accelerometer and the difference in the flow path in the z-axis direction. 4. The inkjet image forming apparatus according to 3 above, wherein the acceleration of the unit is reduced.
5.
a cushioning member that suppresses pressure fluctuations of the ink is provided in the flow path;
The control means may frequency-analyze the acceleration detected by the accelerometer, and calculate the total value using the remaining acceleration components after excluding acceleration components in a frequency band in which pressure fluctuations are suppressed by the cushioning member. 5. The inkjet image forming apparatus according to 2 or 4 above, characterized by:
6.
driving means for bringing the carriage unit closer to the recording medium are arranged on both end sides of the carriage unit,
When the timing at which the carriage unit moves to and stops at the predetermined printing position differs by a predetermined time or longer at both ends of the carriage unit, the acceleration by the driving means on the side that stops first is reduced. 6. The inkjet image forming apparatus according to 2, 4 or 5.
7.
Acceleration detection results are input from an accelerometer capable of measuring acceleration in two orthogonal xy-axis directions mounted on a carriage unit mounted with an ink ejection section and a flow path member constituting a flow path for supplying ink to the ink ejection section. ,
A sensor for detecting a defective portion of an image formed on a recording medium inputs whether or not there is a defective portion,
A control device for controlling a driving means for moving the carriage unit to a predetermined printing position during printing,
The product of the acceleration in the x-axis direction detected by the accelerometer and the flow difference in the x-axis direction and the product of the acceleration in the y-axis direction and the flow difference in the y-axis direction detected by the accelerometer are calculated. When the total value exceeds a predetermined threshold value, the driving means is controlled to reduce the acceleration of the carriage unit, thereby recovering the state in which air enters the nozzles of the ink ejection section. A control device for an ink jet image forming apparatus, wherein a test chart is printed after the test chart is printed, and printing is executed if the defective portion does not occur.
8.
Acceleration detection results are input from an accelerometer capable of measuring acceleration in orthogonal xyz three-axis directions mounted on a carriage unit mounted with an ink ejection portion and a passage member constituting a passage for supplying ink to the ink ejection portion. ,
A sensor for detecting a defective portion of an image formed on a recording medium inputs whether or not there is a defective portion,
A control device for controlling a driving means for moving the carriage unit to a predetermined printing position during printing,

the product of the acceleration in the x-axis direction detected by the accelerometer and the flow difference in the x-axis direction, and the product of the acceleration in the y-axis direction and the flow difference in the y-axis direction detected by the accelerometer; The product of the acceleration in the z-axis direction detected by the accelerometer and the difference in the flow path in the z-axis direction is summed, and when the sum exceeds a predetermined threshold, the driving means is controlled. The acceleration of the carriage unit is reduced to recover the state in which air is in the nozzles of the ink ejection section, and then the test chart is printed. A control device for an inkjet image forming apparatus.
9.
9. The method according to 7 or 8 above, wherein when the total value exceeds the threshold a predetermined number of times, the total value calculated after decreasing the acceleration of the carriage unit is updated as a new threshold. control device for an inkjet image forming apparatus.

According to the present invention, the inkjet image forming apparatus and the control of the inkjet image forming apparatus can accurately grasp the pressure fluctuation of the ink in the flow path leading to the nozzles by measuring the acceleration of the carriage unit on which the inkjet head is mounted. Equipment can be provided.

Schematic diagram showing the overall configuration of an inkjet image forming apparatus according to an embodiment FIG. 2 is a block diagram showing the inkjet image forming apparatus shown in FIG. 1; 2 is a perspective view showing a carriage unit of the inkjet image forming apparatus shown in FIG. 1; FIG. Schematic diagram showing an ink flow path of the inkjet image forming apparatus shown in FIG. FIG. 2 is a sectional view showing an ink flow path of the inkjet image forming apparatus shown in FIG. 1; Flowchart showing the operation of the inkjet image forming apparatus shown in FIG. 2 is a flowchart showing another example of the operation of the inkjet image forming apparatus shown in FIG. 1;

Hereinafter, an inkjet image forming apparatus and a control device for the inkjet image forming apparatus according to embodiments of the present invention will be described with reference to the drawings. However, the scope of the invention is not limited to the illustrated examples. In the following description, parts having the same functions and configurations are denoted by the same reference numerals, and their description may be omitted.

FIG. 1 is a schematic diagram showing the overall configuration of an inkjet image forming apparatus according to an embodiment.
FIG. 2 is a block diagram showing the inkjet image forming apparatus shown in FIG.
In FIG. 1 and each figure to be described later, the descending and clamping direction (ink ejection direction) of the carriage unit 24 is shown as the x-axis, the horizontal movement direction of the carriage unit 24 as the y-axis, and the conveying direction of the axial recording medium P as the z-axis. there is These xyz three axes are orthogonal to each other. These xyz three axes may be set in any direction with respect to the inkjet image forming apparatus.

The inkjet image forming apparatus 1 includes a paper feeding section 10, an image forming section 20, a paper discharging section 30, and a control section 40, as shown in FIGS. In the inkjet image forming apparatus 1, the image forming section 20 forms an image on the recording medium P conveyed from the paper feeding section 10 to the image forming section 20 by controlling each section by the control section 40. The recording medium P is discharged to the paper discharge section 30 .

As shown in FIG. 1 , the paper feeding section 10 holds a recording medium P on which an image is to be formed, and supplies the recording medium P to the image forming section 20 . The paper feed section 10 has a paper feed tray 11 and a transport section 12 .

The paper feed tray 11 is a plate-like member provided so that one or a plurality of recording media P can be stacked and placed. The paper feed tray 11 is provided so as to move up and down according to the amount of the recording medium P placed thereon, and is held at a position where the recording medium P is transported by the transport unit 12 .

The transport unit 12 includes a transport mechanism that rotationally drives a ring-shaped belt 123 with a plurality of rollers 121 and 122 to transport the recording medium P on the belt 123, and a transport mechanism that transports the recording medium P placed on the paper feed tray 11 to the belt. 123 has a supply. The conveying unit 12 conveys the recording medium P transferred to the belt 123 by the supply unit by rotating the belt 123 .

The image forming section 20 ejects ink onto the transported recording medium P to form an image. The image forming section 20 has a transfer unit 22 , a sheet heating section 23 , an image forming drum 21 , a carriage unit 24 , an irradiation section 25 and a delivery section 26 .

The transfer unit 22 is provided at a position between the conveying section 12 of the paper feeding section 10 and the image forming drum 21 , and transfers the recording medium P conveyed by the conveying section 12 to the image forming drum 21 .

The paper heating section 23 heats the recording medium P carried by the image forming drum 21 . The paper heating unit 23 has, for example, an infrared heater (a carbon heater, a far-infrared sheathed heater, a ceramic heater, a halogen lamp heater, a quartz tube heater, etc.) and the like, and generates heat when energized. The paper heating unit 23 is provided in the vicinity of the outer peripheral surface of the image forming drum 21 and upstream of the carriage unit 24 in the conveying direction of the recording medium P by the rotation of the image forming drum 21 . As shown in FIG. 2, the paper heating unit 23 controls its heat generation by a control unit 40 so that the recording medium P carried by the image forming drum 21 and passing near the paper heating unit 23 reaches a predetermined temperature. be done.

As shown in FIG. 1, the image forming drum 21 carries the recording medium P along its cylindrical outer peripheral surface and conveys the recording medium P by being rotated. The conveying surface of the image forming drum 21 faces the sheet heating section 23, the carriage unit 24, and the irradiation section 25, so that the conveyed recording medium P is sequentially subjected to image formation processing.

As shown in FIG. 2, the control unit 40 outputs a display signal to a display device 41 such as an LCD to perform a predetermined display. A memory 42 is connected to the controller 40 and stores necessary information. Furthermore, an in-line sensor 245 is connected to the control section 40 so that a defective portion of the image formed on the recording medium P can be detected.

3 is a perspective view showing a carriage unit of the inkjet image forming apparatus shown in FIG. 1. FIG.

As shown in FIG. 3, the carriage unit 24 is constructed by mounting an inkjet head 242 on a movable carriage 241 . The inkjet head 242 has nozzles (not shown) serving as ink ejection portions. A plurality of nozzles are formed on the nozzle surface, which is the lower surface of the inkjet head 242 . The inkjet head 242 ejects ink from nozzles onto the recording medium P carried on the image forming drum 21 to form an image. The direction of ink ejection from the nozzles is toward the center of the image forming drum 21, as shown in FIG. 1, and is not limited to the vertically downward direction. The carriage unit 24 is mounted with a channel member that constitutes an ink channel that supplies ink to the nozzles of the inkjet head 242 . The ink flow path is laid and bent in all directions of the xyz three axes through a tube, which is a flow path member, a block in which the flow path is bored, and the like.

Carriage units 24 are individually provided for each of the colors C (cyan), M (magenta), Y (yellow), and K (black). In FIG. 1, carriage units 24 corresponding to the respective colors of Y, M, C, and K are sequentially provided from upstream in the conveying direction of the recording medium P conveyed by rotation of the image forming drum 21 .

The inkjet head 242 is provided with a length (width) that covers the entire width of the recording medium P in the direction perpendicular to the conveying direction of the recording medium P (width direction). That is, the inkjet image forming apparatus 1 in this embodiment is a one-pass inkjet image forming apparatus. The carriage unit 24 can be configured as a line head by arranging a plurality of inkjet heads 242 . The inkjet 242 may be a head that employs any of various drive schemes.

The carriage unit 24 is provided with a carriage driving section 243 serving as driving means (not shown) for horizontally moving the carriage unit 24 toward a predetermined printing position during printing and driving means for lowering or obliquely lowering the carriage unit 24 . A carriage drive unit 243 is an air cylinder, a motor, or the like. The predetermined print position is a position facing and close to the image forming drum 21, and in this embodiment, it is reached by horizontally moving from the standby position and then descending or obliquely descending. The carriage driving section 243 is arranged on both end sides of the carriage unit 24 in this embodiment. However, only one carriage driving section 243 may be provided for one carriage unit 24 . The carriage driving section 243 is controlled by the control section 40 so that the acceleration of the carriage unit 24 has a desired value, as shown in FIG.

In this embodiment, the carriage unit 24 is equipped with an accelerometer 244 capable of measuring acceleration in three orthogonal xyz-axis directions. Accelerometer 244 may be of any type and configuration known in the art. This accelerometer 244 can measure acceleration in any direction, including the direction parallel to the ink flow path. However, as will be described later, in the case where the movement direction of the carriage unit 24 is in two orthogonal axial directions, if the xy two axial directions are made to coincide with these moving directions, the accelerometer 244 can be detected only in the orthogonal xy two axial directions. Acceleration can be measured. Acceleration detection results (acceleration values) measured by the accelerometer 244 are input to the control unit 40 as shown in FIG.

As shown in FIG. 1, the irradiation unit 25 irradiates the recording apparatus P with an energy beam for curing the ink after the carriage unit 24 ejects the ink onto the recording medium P. As shown in FIG. The irradiation unit 25 has, for example, a fluorescent tube such as a low-pressure mercury lamp, and emits energy rays such as ultraviolet rays by causing the fluorescent tube to emit light. The irradiation unit 25 is provided in the vicinity of the outer peripheral surface of the image forming drum 21 and downstream of the carriage unit 24 in the direction in which the recording medium P is conveyed by the rotation of the image forming drum 21 . The irradiation unit 25 irradiates the recording medium P carried by the image forming drum 21 onto which ink has been discharged, with energy rays, and cures the ink discharged onto the recording medium P by the action of the energy rays. The irradiation unit 25 is controlled by the control unit 40 as shown in FIG.

The ink used in the inkjet image forming apparatus 1 of the present embodiment is not particularly limited, but is, for example, an ultraviolet (UV) curable ink. Fluorescent tubes that emit ultraviolet rays include, in addition to low-pressure mercury lamps, mercury lamps with an operating pressure of several hundred Pa to 1 MPa, light sources that can be used as germicidal lamps, cold cathode tubes, ultraviolet laser light sources, metal halide lamps, light-emitting diodes, etc. is mentioned. Among these, a light source (for example, a light-emitting diode, etc.) that can irradiate ultraviolet light with a higher illuminance and consumes less power is desirable. Moreover, the energy beam is not limited to ultraviolet rays, and any energy beam having the property of curing the ink according to the properties of the ink may be used, and the light source can also be selected according to the wavelength of the energy beam.

As shown in FIG. 1, the delivery section 26 conveys the recording medium P irradiated with the energy beams from the irradiation section 25 from the image forming drum 21 to the paper discharge section 30 . The delivery unit 26 includes a transport mechanism that rotates a ring-shaped belt 263 by a plurality of rollers 261 and 262 to transport the recording medium P on the belt 263, and a cylinder that transfers the recording medium P from the image forming drum 21 to the transport mechanism. It has a shaped transfer drum 264 and the like. The delivery section 26 transports the recording medium P delivered to the belt 263 by the delivery drum 264 by the belt 263 and delivers it to the paper ejection section 30 .

The paper discharge section 30 stores the recording medium P delivered from the image forming section 20 by the delivery section 26 . The paper discharge unit 30 has a plate-like paper discharge tray 31 and the like, and the recording medium P after image formation is stacked on the paper discharge tray 31 .

FIG. 4 is a schematic diagram showing ink flow paths of the inkjet image forming apparatus shown in FIG.
FIG. 5 is a cross-sectional view showing ink flow paths of the inkjet image forming apparatus shown in FIG.

In the inkjet image forming apparatus 1 of the present embodiment, as shown in FIGS. 4 and 5, the ink pumped from the main ink tank 51 by the supply pump 52 is supplied to the first ink flow path 53 of each carriage unit 24 . It is supplied to the sub-tank 54 .

The ink flow path 53 is a circulation path so that ink that has not been ejected from each carriage unit 24 can be returned to the first sub-tank 54 as necessary. The ink in the first sub-tank 54 is sent to the second sub-tank 57 via the liquid sending pump 55 and the check valve 56 . The ink sent to the second sub-tank 57 is supplied to the inlet 242 a of the inkjet head 242 .

In the inkjet head 242, the ink supplied to the inlet 242a is stored in a hollow manifold 246 as shown in FIG. The interior of this manifold 246 is part of the ink flow path 53 . A bottom surface of the manifold 246 is closed by a nozzle plate 247 having a plurality of nozzles. The lower surface of the nozzle plate 247 is the nozzle surface. A plurality of pressure chambers (not shown) are provided in the manifold 246 corresponding to each nozzle. Ink injected into the pressure chambers from the manifold 246 is ejected from the nozzles due to the electromechanical conversion action of the piezoelectric elements forming the pressure chambers. A negative pressure is applied to the ink inside the nozzle, and together with the surface tension of the ink, the ink resists gravity and stays inside the nozzle.

The interior of manifold 246 is separated into an upper chamber and a lower chamber by filter 248 . The filter 248 removes dust and air bubbles in the ink and allows the ink to pass from the upper chamber to the lower chamber. Further, dampers 249 are provided in the manifold 246 so as to function as cushioning members that are positioned above the respective pressure chambers and suppress pressure fluctuations of the ink.

The ink that has passed through the upper chamber of the manifold 246 of the inkjet head 242 supplied with ink from the second sub-tank 57 is supplied to the inlet 242a of the other inkjet head 242 from the outlet 242b. Ink from the other inkjet heads 242 also passes through the upper chamber and is returned to the first sub-tank 54 from the outlet 242b. Ink that has not been discharged through the lower chamber of the manifold 246 of the inkjet head 242 supplied with ink from the second sub-tank 57 is returned to the first sub-tank 54 through the second outlet 242c. In other inkjet heads 242 as well, ink that has not been ejected through the lower chamber is returned to the first sub-tank 54 through the second outlet 242c.

In this image forming apparatus 1, the carriage unit 24 does not move during image formation, and is operated to move from a standby position to a predetermined print position by a driving means before image formation. This movement consists of horizontal movement indicated by arrow y in FIGS. 3 to 5, downward movement indicated by arrow x (movement to approach image forming drum 21), and position fixing action (clamping). . The carriage unit 24 does not move in the transport direction of the recording medium P indicated by the arrow z.

When the carriage unit 24 is moved, the ink flow path 53 is vibrated or impacted, and the kinetic energy is converted into pressure fluctuations, causing pressure fluctuations in the ink in the ink flow path 53 . Ink pressure fluctuations occur in conjunction with the acceleration of the carriage unit 24 . This force F is represented by [F=ma] (∵m: weight of ink, a: acceleration of ink) from the equation of motion.

When the force F applied to the ink is greater than a predetermined value, that is, when the pressure fluctuation of the ink is greater than a predetermined value, a meniscus break occurs, causing the ink in the nozzle to retreat inward and air to enter the nozzle. enters. If air enters the nozzles in this manner, ink cannot be ejected, resulting in defective printing (missing dots).

In the carriage unit 24, the ink flow path 53 is laid and bent in all directions of the xyz three axes through a tube as a flow path member, a block in which the flow path is formed, and the like. The force F applied to the ink in the ink flow path 53 is expressed as follows.

F=Σma=mx·ax+my·ay+mz·az
(∵ax: x-axis component of acceleration a, ay: y-axis component of acceleration a, az: z-axis component of acceleration a, mx: dynamic pressure contribution of ink mass m in the x-axis direction, my: ink dynamic pressure contribution of mass m in the y-axis direction, mz: dynamic pressure contribution of ink mass m in the z-axis direction)

The weight m of ink is represented by [m=LSρ] (∵L: length of ink channel, S: cross-sectional area of ink channel, ρ: specific gravity of ink).
The length L of the ink flow path is the distance along the ink flow path 53 from the start point to the end point of the ink flow path 53. If the second sub-tank 57 has an ink interface (liquid surface), this It indicates from the interface to the nozzle surface, and if there is no interface, it indicates from the liquid feed pump (negative pressure pump) 55 to the nozzle surface.

The force F is expressed as follows.
F=Sρ(Lx·ax+Ly·ay+Lz·az)
(∵Lx: x-axis component of L, Ly: y-axis component of L, Lz: z-axis component of L)
Assuming that the pressure fluctuation is ΔP, the forces F due to the components of Lx, Ly, and Lz in opposite directions cancel each other out, so ΔP is expressed as follows.
ΔP=ρ(ΔLx・ax+ΔLy・ay+ΔLz・az)
(∵ΔLx: x-axis direction flow path difference, ΔLy: y-axis direction flow path difference, ΔLz: z-axis direction flow path difference)
The x-axis direction flow path difference is the distance in the x-axis direction (the x-axis component of the linear distance) between the start point and the end point of the ink flow path 53, and the y-axis direction flow path difference is the start point and the end point of the ink flow path 53. is the distance in the y-axis direction (y-axis component of the linear distance), and the z-axis direction channel difference is the distance in the z-axis direction (z-axis component of the linear distance) between the start point and the end point of the ink channel 53 .
That is, the pressure variation ΔP is expressed as a function of the acceleration a.

As shown in FIG. 5, in the embodiment, the x-axis direction flow path difference ΔLx is the vertical distance (elevation difference) from the interface of the ink in the second sub-tank 57 to the nozzle surface. The flow path difference ΔLy is the horizontal distance from the center position of the ink flow path from the second sub-tank 57 to the farthest position on the nozzle surface, and the z-axis direction flow path difference ΔLz is the ink flow from the second sub-tank 57. It is the horizontal distance from the center of the channel to the furthest point on the nozzle face.

The control means 40 controls the product (ΔLx·ax) of the acceleration ax in the x-axis direction and the difference ΔLx in the x-axis direction and the product (ΔLy·ay ) and the product (ΔLz az) of the acceleration az in the z-axis direction and the flow path difference ΔLz in the z-axis direction, and this total value (ρ (ΔLx ax + ΔLy ay + ΔLz az) = ΔP) is predetermined If the threshold is exceeded, the acceleration a of the carriage unit 24 is reduced.

When the accelerometer 244 measures acceleration only in two orthogonal xy-axis directions, the control unit 40 calculates the product of the x-axis direction acceleration ax and the x-axis direction flow path difference ΔLx (ΔLx·ax ) and the product (ΔLy·ay) of the acceleration ay in the y-axis direction and the y-axis direction flow path difference ΔLy, and this total value (ρ(ΔLx·ax+ΔLy·ay)=ΔP) is a predetermined threshold value is exceeded, the acceleration a of the carriage unit 24 is decreased.

Reducing the acceleration a of the carriage unit 24 specifically causes the control means 40 to lower the outputs of the driving means (horizontal movement) and the carriage driving section 243 (lowering), thereby slowing down the movement speed of the carriage unit 24. It can be done by

FIG. 6 is a flow chart showing the operation of the inkjet image forming apparatus shown in FIG.

As shown in FIG. 6, when starting the process, the control unit 40 issues a print instruction in step st1. In the next step st2, the carriage unit 24 is moved to the printing position. In the next step st3, the pressure fluctuation ΔP (=ρ(ΔLx·ax+ΔLy·ay+ΔLz·az)) occurring in the ink in the ink flow path 53 when the carriage unit 24 is moved is calculated.

At the next step st4, it is determined whether or not the pressure fluctuation ΔP exceeds the threshold value. At step st5, printing is executed and the process is terminated.

At step st6, the acceleration of the carriage unit 24 is lowered by one step. In the next step st7, the test chart is printed after recovering from the large shortage (the state in which air is in the nozzle). In the next step st8, the in-line sensor 245 determines whether or not there is a large shortage (ejection failure due to air entering the nozzle). proceed to

In this inkjet image forming apparatus 1, the product of each axial component (ax, ay, az) of the acceleration a of the carriage unit 24 and each direction flow path difference (ΔLx, ΔLy, ΔLz) of the ink flow path 53 is summed up. , this total value (ρ(ΔLx·ax+ΔLy·ay+ΔLz·az)=ΔP) is compared with a predetermined threshold value, so it is possible to perform a highly accurate determination that is closer to the actual phenomenon. If there is no dropout, the acceleration of the carriage unit 24 is not reduced more than necessary, so the waiting time until printing can be shortened.

It should be noted that the pressure variation ΔP (calculated value) exceeds the threshold value while the inkjet image forming apparatus 1 is being used due to abrasion of the mechanical portion of the carriage driving portion 243 or the like.

FIG. 7 is a flow chart showing another example of the operation of the inkjet image forming apparatus shown in FIG.

In the flowchart shown in FIG. 6, the control unit 40 determines whether or not there is a large shortage (ejection failure due to air entering the nozzle) using the in-line sensor 245 in step st8 described above, as shown in FIG. If it is discriminated and it has occurred, it may return to step st6, and if it has not occurred, it may proceed to step st9.

At step st9, it is determined whether or not the number of times the pressure fluctuation ΔP (calculated value) exceeds the threshold at step st4 exceeds a predetermined number of times (n times). proceed to

At step st10, the pressure variation ΔP calculated after the acceleration of the carriage unit 24 is decreased is updated and stored as a new threshold, and the process proceeds to step st5.

By updating the threshold value in this manner, the acceleration of the carriage unit 24 is reliably maintained in a state in which no large shortage occurs. The reason why such updating of the threshold value is necessary is that bubbles exist in the ink in the ink flow path 53 at the beginning of use of the inkjet image forming apparatus 1, and the bubbles act as buffers against acceleration. This is because the actual pressure fluctuation ΔP is smaller than the calculated value and the threshold is set high. As the ink jet image forming apparatus 1 is used, bubbles in the ink are degassed, and the actual pressure fluctuation ΔP increases with respect to the acceleration. It becomes impossible to suppress within the value.

In the ink jet image forming apparatus 1, a viscoelastic element, such as a vibration interference between adjacent nozzles in the manifold 246, absorbs a specific frequency band component of pressure fluctuation in the ink flow path 53 and suppresses the pressure fluctuation. If there is a damper such as a damper 249 for reducing the frequency band absorbed by this damper overlaps the frequency band of the acceleration detected by the accelerometer 244, frequency discrimination of the detected acceleration a is performed. is preferred.

In the inkjet image forming apparatus 1 of this embodiment, a damper 249 serving as a cushioning member for suppressing pressure fluctuations of ink is provided inside the ink flow path 53 (inside the manifold 246).

When a damper 249 is provided in the manifold 246, this damper 249 absorbs high-frequency band components (for example, 30 Hz or higher) of ink pressure fluctuations. When the carriage unit 24 moves horizontally and descends (moves at a substantially constant speed), the ink pressure fluctuation is mainly composed of low-frequency components, so the damper 249 hardly suppresses it. At the end of movement of the carriage unit 24 and at the time of position fixing operation (clamping), ink pressure fluctuations include high frequency band components (for example, 30 Hz or higher), and these high frequency band components are suppressed by the damper 249 .

Therefore, the operation of reducing the acceleration a of the carriage unit 24 is preferably performed based on pressure fluctuations in the frequency band (low frequency band in this embodiment) that is not suppressed by the damper 249 . That is, the control means 40 performs frequency analysis (for example, Fourier analysis) on the acceleration detected by the accelerometer 244, removes the acceleration component in the frequency band in which the pressure fluctuation is suppressed by the damper 249, and sums the remaining acceleration components. A value calculation is preferably performed. This prevents the acceleration of the carriage unit 24 from being reduced more than necessary due to the acceleration component in the frequency band whose pressure fluctuation is suppressed by the damper 249 .

In the ink jet image forming apparatus 1, when the timing at which the carriage unit 24 is moved to a predetermined printing position and stopped is different for a predetermined time or more between the two ends of the carriage unit 24, the carriage drive unit that stops first It is preferable to reduce the acceleration due to 243.

As described above, in the case where the carriage driving section 243 is provided at both ends of the carriage unit 24, if the timings at which the carriage unit 24 is moved to the printing position and stopped differ by a certain time or more at both ends of the carriage unit 24, This means that the acceleration by the carriage drive unit 243 on the side to stop is greater than the acceleration by the carriage drive unit 243 on the side to stop later by a certain value or more. Therefore, in this case, the acceleration imbalance at both ends of the carriage unit 24 can be eliminated by reducing the acceleration of the carriage driving section 243 that stops first.

Note that when the difference between the timings at which the carriage unit 24 is moved to the printing position and stops at both ends of the carriage unit 24 is less than a certain time, the acceleration by the carriage driving unit 243 is reduced. Acceleration by the carriage drive units 243, 243 is reduced at the same time.

The specific configurations, shapes, materials, operations, numerical values, etc. in the description of the above embodiments are merely examples for describing the present invention, and the present invention should not be construed as being limited by these. not.

In the ink jet image forming apparatus described above, four carriage units 24 are provided for each of the colors C, M, Y, and K. A larger number of inkjet heads may be provided to correspond to different colors.

Further, in the inkjet image forming apparatus described above, the recording device P is conveyed by the rotation of the image forming drum 21, but a belt, roller, or the like is used to convey the recording device P while maintaining it in a flat state. good too.

Although the inkjet image forming apparatus described above is of the one-pass type, it may be of a scanning type in which the inkjet head is scanned.

Furthermore, although the inkjet image forming apparatus described above uses ultraviolet curable ink, the ink is not particularly limited, and pigment ink and other various inks may be used.

1 Inkjet image forming apparatus 10 Paper feed unit 11 Paper feed tray 12 Conveying unit 121 Roller 122 Roller 123 Belt 20 Image forming unit 21 Image forming drum 22 Delivery unit 23 Paper heating unit 24 Carriage unit 241 Carriage 242 Ink jet head 242a Inlet 242b Outlet 242c Outlet 243 Carriage drive unit 244 Accelerometer 245 Inline sensor 246 Manifold 247 Nozzle plate 248 Filter 249 Damper 25 Irradiation unit 26 Delivery unit 261 Roller 262 Roller 263 Belt 264 Transfer drum 30 Paper discharge unit 31 Paper discharge tray 40 Control unit 41 Display device 42 Memory 51 Main ink tank 52 Supply pump 53 Ink channel 54 First sub-tank 55 Liquid sending pump 56 Check valve 57 Second sub-tank

Claims (7)

a carriage unit mounted with an ink ejecting portion and a channel member forming a channel for supplying ink to the ink ejecting portion;
a driving means for moving the carriage unit to a predetermined printing position during printing ;
and a control means for controlling the driving means ,
The carriage unit is equipped with an accelerometer capable of measuring acceleration in two orthogonal xy-axis directions ,
The control means controls the product of the acceleration in the x-axis direction detected by the accelerometer and the flow difference in the x-axis direction, and the acceleration in the y-axis direction and the flow difference in the y-axis direction detected by the accelerometer. and the product of , and when the sum exceeds a predetermined threshold value, the acceleration of the carriage unit is reduced . a carriage unit mounted with an ink ejecting portion and a channel member forming a channel for supplying ink to the ink ejecting portion;
a driving means for moving the carriage unit to a predetermined printing position during printing ;
and a control means for controlling the driving means ,
The carriage unit is equipped with an accelerometer capable of measuring acceleration in three orthogonal xyz-axis directions ,
The control means controls the product of the acceleration in the x-axis direction detected by the accelerometer and the flow difference in the x-axis direction, and the acceleration in the y-axis direction and the flow difference in the y-axis direction detected by the accelerometer. and the product of the acceleration in the z-axis direction detected by the accelerometer and the difference in the flow path in the z-axis direction. An inkjet image forming apparatus characterized by reducing unit acceleration . a cushioning member that suppresses pressure fluctuations of the ink is provided in the flow path;
The control means may frequency-analyze the acceleration detected by the accelerometer, and calculate the total value using the remaining acceleration components after excluding acceleration components in a frequency band in which pressure fluctuations are suppressed by the cushioning member. 3. The inkjet image forming apparatus according to claim 1 or 2 , characterized by: driving means for bringing the carriage unit closer to the recording medium are arranged on both end sides of the carriage unit,
When the timing at which the carriage unit moves to and stops at the predetermined printing position differs by a predetermined time or more between the two ends of the carriage unit, the acceleration by the driving means on the side that stops first is reduced. 4. The inkjet image forming apparatus according to Item 1, 2 or 3 . Acceleration detection results are input from an accelerometer capable of measuring acceleration in two orthogonal xy-axis directions mounted on a carriage unit mounted with an ink ejection section and a flow path member constituting a flow path for supplying ink to the ink ejection section. ,
A sensor for detecting a defective portion of an image formed on a recording medium inputs whether or not there is a defective portion,
A control device for controlling a driving means for moving the carriage unit to a predetermined printing position during printing,
The product of the acceleration in the x-axis direction detected by the accelerometer and the flow difference in the x-axis direction and the product of the acceleration in the y-axis direction and the flow difference in the y-axis direction detected by the accelerometer are calculated. When the total value exceeds a predetermined threshold value, the driving means is controlled to reduce the acceleration of the carriage unit, thereby recovering the state in which air enters the nozzles of the ink ejection section. A control device for an ink jet image forming apparatus, wherein a test chart is printed after the test chart is printed, and printing is executed if the defective portion does not occur. Acceleration detection results are input from an accelerometer capable of measuring acceleration in orthogonal xyz three-axis directions mounted on a carriage unit mounted with an ink ejection portion and a passage member constituting a passage for supplying ink to the ink ejection portion. ,
A sensor for detecting a defective portion of an image formed on a recording medium inputs whether or not there is a defective portion,
A control device for controlling a driving means for moving the carriage unit to a predetermined printing position during printing,
the product of the acceleration in the x-axis direction detected by the accelerometer and the flow difference in the x-axis direction, and the product of the acceleration in the y-axis direction and the flow difference in the y-axis direction detected by the accelerometer; The product of the acceleration in the z-axis direction detected by the accelerometer and the difference in the flow path in the z-axis direction is summed, and when the sum exceeds a predetermined threshold, the driving means is controlled. The acceleration of the carriage unit is reduced to recover the state in which air is in the nozzles of the ink ejection section, and then the test chart is printed. A control device for an inkjet image forming apparatus. 7. When the total value exceeds the threshold value for a predetermined number of times, the total value calculated after reducing the acceleration of the carriage unit is updated as a new threshold value. A controller for the described inkjet image forming apparatus.

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